Stepped waveform VSCF system with engine start capability

Abstract

A power converter that can be used either as a start converter or as a variabe speed constant frequency converter is utilized within a stepped waveform VSCF system having engine start capability. Interfacing with the converter are a load bus, a contactor, a field excitation controller and a starter/generator having a main generator, an exciter generator and a permanent magnet generator. Magnetic components and semiconductor components perform multi-functions and minimal degradation of input power quality occurs.

We claim: 
     
       1. A stepped waveform VSCF system with engine start capability comprising: starter/generator means mounted to an engine;   converter means connected to said starter/generator means and including a plurality of DC/AC inverters connected to said starter/generator means, a plurality of high frequency trap-tuned filters connected to contactor means, three phase transformer means connected between said plurality of high frequency trap-tuned filters and said plurality of DC/AC inverters for providing isolation, and filter capacitor means connected across said plurality of DC/AC inverters;   field excitation controller means connected to said starter/generator means;   control power supply means connected to said field excitation controller means;   said contactor means connected to said converter means;   load bus means connected to said contactor means;   said three phase transformer means including secondary winding means connected to said plurality of high frequency trap-tuned filters and primary winding means connected to said plurality of DC/AC inverters;   said converter means including timing logic means for switching on and off at a desired frequency, each of a plurality of semiconductor switches to produce a multiple step three-phase output voltage at said secondary winding means of said three phase transformer means;   said converter means further including PWM controller means connected to said control power supply means;   resolver means connected between said starter/generator means and said PWM controller means; and   back EMF sensor circuit means connected to said PWM controller means.   
     
     
       2. A stepped waveform VSCF system with engine start capability as claimed in claim 1 wherein said starter/generator means comprises: permanent magnet generator means connected to said engine;   exciter generator means connected to said permanent magnet generator means and to said field excitation controller means; and,   main generator means connected to said exciter generator means and to said converter means.   
     
     
       3. A stepped waveform VSCF system with engine start capability as claimed in claim 2 wherein said permanent magnet generator means provides power to said field excitation controller means which influences excitation of exciter of said exciter generator means within said starter/generator means. 
     
     
       4. A stepped waveform VSCF system with engine start capability as claimed in claim 1 wherein each of said plurality of DC/AC inverters comprises: a plurality of semiconductor switches having associated flywheel rectifiers or diodes.   
     
     
       5. A stepped waveform VSCF system with engine start capability as claimed in claim 1 wherein said converter means can be used as a start converter. 
     
     
       6. A stepped waveform VSCF system with engine start capability as claimed in claim 1 wherein said converter means can be used as a variable speed constant frequency converter. 
     
     
       7. A stepped waveform VSCF system with engine start capability as claimed in claim 1 wherein said converter means can be used as a start converter and as a variable speed constant frequency converter causing minimal degradation of input power quality. 
     
     
       8. A stepped waveform VSCF system with engine start capability as claimed in claim 1 wherein said converter means comprises: five DC/AC three-phase inverters connected to said starter/generator means;   three high frequency trap-tuned filters connected to said contactor means;   three phase transformer means connected between said three high frequency trap-tuned filters and said five DC/AC converters for providing isolation; and,   filter capacitor means connected across said five DC/AC converters.   
     
     
       9. A stepped waveform VSCF system with engine start capability as claimed in claim 8 wherein each of said five DC/AC inverters comprises: six semiconductor switches having associated flywheel rectifiers or diodes.   
     
     
       10. A stepped waveform VSCF system with engine start capability as claimed in claim 9 wherein said three phase transformer means comprises: said secondary winding means connected to said three high frequency trap-tuned filters; and,   said primary winding means connected to four of said five DC/AC inverters.   
     
     
       11. A stepped waveform VSCF system with engine start capability as claimed in claim 10 wherein said converter means further comprises: said timing logic means for switching on and off at the desired frequency, each of said six semiconductor switches to produce a twenty-four step three-phase AC output voltage at said secondary winding means of said three-phase transformer means.